==============
Django Tagging
==============
A generic tagging application for `Django`_ projects, which allows
association of a number of tags with any Django model instance and makes
retrieval of tags simple.
.. _`Django`: http://www.djangoproject.com
.. contents::
:depth: 3
Installation
============
Installing an official release
------------------------------
Official releases are made available from
http://code.google.com/p/django-tagging/
Source distribution
~~~~~~~~~~~~~~~~~~~
Download the .zip distribution file and unpack it. Inside is a script
named ``setup.py``. Enter this command::
python setup.py install
...and the package will install automatically.
Windows installer
~~~~~~~~~~~~~~~~~
A Windows installer is also made available - download the .exe
distribution file and launch it to install the application.
An uninstaller will also be created, accessible through Add/Remove
Programs in your Control Panel.
Installing the development version
----------------------------------
Alternatively, if you'd like to update Django Tagging occasionally to pick
up the latest bug fixes and enhancements before they make it into an
official release, perform a `Subversion`_ checkout instead. The following
command will check the application's development branch out to an
``tagging-trunk`` directory::
svn checkout http://django-tagging.googlecode.com/svn/trunk/ tagging-trunk
Add the resulting folder to your `PYTHONPATH`_ or symlink (`junction`_,
if you're on Windows) the ``tagging`` directory inside it into a
directory which is on your PYTHONPATH, such as your Python
installation's ``site-packages`` directory.
You can verify that the application is available on your PYTHONPATH by
opening a Python interpreter and entering the following commands::
>>> import tagging
>>> tagging.VERSION
(0, 3, 'pre')
When you want to update your copy of the Django Tagging source code, run
the command ``svn update`` from within the ``tagging-trunk`` directory.
.. caution::
The development version may contain bugs which are not present in the
release version and introduce backwards-incompatible changes.
If you're tracking trunk, keep an eye on the `CHANGELOG`_ and the
`backwards-incompatible changes wiki page`_ before you update your
copy of the source code.
.. _`Subversion`: http://subversion.tigris.org
.. _`PYTHONPATH`: http://www.python.org/doc/2.5.2/tut/node8.html#SECTION008120000000000000000
.. _`junction`: http://www.microsoft.com/technet/sysinternals/FileAndDisk/Junction.mspx
.. _`CHANGELOG`: http://django-tagging.googlecode.com/svn/trunk/CHANGELOG.txt
.. _`backwards-incompatible changes wiki page`: http://code.google.com/p/django-tagging/wiki/BackwardsIncompatibleChanges
Using Django Tagging in your applications
-----------------------------------------
Once you've installed Django Tagging and want to use it in your Django
applications, do the following:
1. Put ``'tagging'`` in your ``INSTALLED_APPS`` setting.
2. Run the command ``manage.py syncdb``.
The ``syncdb`` command creates the necessary database tables and
creates permission objects for all installed apps that need them.
That's it!
Settings
========
Some of the application's behaviour can be configured by adding the
appropriate settings to your project's settings file.
The following settings are available:
FORCE_LOWERCASE_TAGS
--------------------
Default: ``False``
A boolean that turns on/off forcing of all tag names to lowercase before
they are saved to the database.
MAX_TAG_LENGTH
--------------
Default: ``50``
An integer which specifies the maximum length which any tag is allowed
to have. This is used for validation in the ``django.contrib.admin``
application and in any forms automatically generated using ``ModelForm``.
Registering your models
=======================
Your Django models can be registered with the tagging application to
access some additional tagging-related features.
.. note::
You don't *have* to register your models in order to use them with
the tagging application - many of the features added by registration
are just convenience wrappers around the tagging API provided by the
``Tag`` and ``TaggedItem`` models and their managers, as documented
further below.
The ``register`` function
-------------------------
To register a model, import the ``tagging`` module and call its
``register`` function, like so::
from django.db import models
import tagging
class Widget(models.Model):
name = models.CharField(max_length=50)
tagging.register(Widget)
The following argument is required:
``model``
The model class to be registered.
An exception will be raised if you attempt to register the same class
more than once.
The following arguments are optional, with some recommended defaults -
take care to specify different attribute names if the defaults clash
with your model class' definition:
``tag_descriptor_attr``
The name of an attribute in the model class which will hold a tag
descriptor for the model. Default: ``'tags'``
See `TagDescriptor`_ below for details about the use of this
descriptor.
``tagged_item_manger_attr``
The name of an attribute in the model class which will hold a custom
manager for accessing tagged items for the model. Default:
``'tagged'``.
See `ModelTaggedItemManager`_ below for details about the use of this
manager.
``TagDescriptor``
-----------------
When accessed through the model class itself, this descriptor will return
a ``ModelTagManager`` for the model. See `ModelTagManager`_ below for
more details about its use.
When accessed through a model instance, this descriptor provides a handy
means of retrieving, updating and deleting the instance's tags. For
example::
>>> widget = Widget.objects.create(name='Testing descriptor')
>>> widget.tags
[]
>>> widget.tags = 'toast, melted cheese, butter'
>>> widget.tags
[, , ]
>>> del widget.tags
>>> widget.tags
[]
``ModelTagManager``
-------------------
A manager for retrieving tags used by a particular model.
Defines the following methods:
* ``get_query_set()`` -- as this method is redefined, any ``QuerySets``
created by this model will be initially restricted to contain the
distinct tags used by all the model's instances.
* ``cloud(*args, **kwargs)`` -- creates a list of tags used by the
model's instances, with ``count`` and ``font_size`` attributes set for
use in displaying a tag cloud.
See the documentation on ``Tag``'s manager's `cloud_for_model method`_
for information on additional arguments which can be given.
* ``related(self, tags, *args, **kwargs)`` -- creates a list of tags
used by the model's instances, which are also used by all instance
which have the given ``tags``.
See the documentation on ``Tag``'s manager's
`related_for_model method`_ for information on additional arguments
which can be given.
* ``usage(self, *args, **kwargs))`` -- creates a list of tags used by
the model's instances, with optional usages counts, restriction based
on usage counts and restriction of the model instances from which
usage and counts are determined.
See the documentation on ``Tag``'s manager's `usage_for_model method`_
for information on additional arguments which can be given.
Example usage::
# Create a ``QuerySet`` of tags used by Widget instances
Widget.tags.all()
# Retrieve a list of tags used by Widget instances with usage counts
Widget.tags.usage(counts=True)
# Retrieve tags used by instances of WIdget which are also tagged with
# 'cheese' and 'toast'
Widget.tags.related(['cheese', 'toast'], counts=True, min_count=3)
``ModelTaggedItemManager``
--------------------------
A manager for retrieving model instance for a particular model, based on
their tags.
* ``related_to(obj, queryset=None, num=None)`` -- creates a list
of model instances which are related to ``obj``, based on its tags. If
a ``queryset`` argument is provided, it will be used to restrict the
resulting list of model instances.
If ``num`` is given, a maximum of ``num`` instances will be returned.
* ``with_all(tags, queryset=None)`` -- creates a ``QuerySet`` containing
model instances which are tagged with *all* the given tags. If a
``queryset`` argument is provided, it will be used as the basis for
the resulting ``QuerySet``.
* ``with_any(tags, queryset=None)`` -- creates a ``QuerySet`` containing model
instances which are tagged with *any* the given tags. If a ``queryset``
argument is provided, it will be used as the basis for the resulting
``QuerySet``.
Tags
====
Tags are represented by the ``Tag`` model, which lives in the
``tagging.models`` module.
API reference
-------------
Fields
~~~~~~
``Tag`` objects have the following fields:
* ``name`` -- The name of the tag. This is a unique value.
Manager functions
~~~~~~~~~~~~~~~~~
The ``Tag`` model has a custom manager which has the following helper
methods:
* ``update_tags(obj, tag_names)`` -- updates tags associated with an
object.
``tag_names`` is a string containing tag names with which ``obj``
should be tagged.
If ``tag_names`` is ``None`` or ``''``, the object's tags will be
cleared.
* ``add_tag(obj, tag_name)`` -- associates a tag with an an object.
``tag_name`` is a string containing a tag name with which ``obj``
should be tagged.
* ``get_for_object(obj)`` -- returns a ``QuerySet`` containing all
``Tag`` objects associated with ``obj``.
.. _`usage_for_model method`:
* ``usage_for_model(model, counts=False, min_count=None, filters=None)``
-- returns a list of ``Tag`` objects associated with instances of
``model``.
If ``counts`` is ``True``, a ``count`` attribute will be added to each
tag, indicating how many times it has been associated with instances
of ``model``.
If ``min_count`` is given, only tags which have a ``count`` greater
than or equal to ``min_count`` will be returned. Passing a value for
``min_count`` implies ``counts=True``.
To limit the tags (and counts, if specified) returned to those used by
a subset of the model's instances, pass a dictionary of field lookups
to be applied to ``model`` as the ``filters`` argument.
.. _`related_for_model method`:
* ``related_for_model(tags, Model, counts=False, min_count=None)``
-- returns a list of tags related to a given list of tags - that is,
other tags used by items which have all the given tags.
If ``counts`` is ``True``, a ``count`` attribute will be added to each
tag, indicating the number of items which have it in addition to the
given list of tags.
If ``min_count`` is given, only tags which have a ``count`` greater
than or equal to ``min_count`` will be returned. Passing a value for
``min_count`` implies ``counts=True``.
.. _`cloud_for_model method`:
* ``cloud_for_model(Model, steps=4, distribution=LOGARITHMIC,
filters=None, min_count=None)`` -- returns a list of the distinct
``Tag`` objects associated with instances of ``Model``, each having a
``count`` attribute as above and an additional ``font_size``
attribute, for use in creation of a tag cloud (a type of weighted
list).
``steps`` defines the number of font sizes available - ``font_size``
may be an integer between ``1`` and ``steps``, inclusive.
``distribution`` defines the type of font size distribution algorithm
which will be used - logarithmic or linear. It must be either
``tagging.utils.LOGARITHMIC`` or ``tagging.utils.LINEAR``.
To limit the tags displayed in the cloud to those associated with a
subset of the Model's instances, pass a dictionary of field lookups to
be applied to the given Model as the ``filters`` argument.
To limit the tags displayed in the cloud to those with a ``count``
greater than or equal to ``min_count``, pass a value for the
``min_count`` argument.
* ``usage_for_queryset(queryset, counts=False, min_count=None)`` --
Obtains a list of tags associated with instances of a model contained
in the given queryset.
If ``counts`` is True, a ``count`` attribute will be added to each tag,
indicating how many times it has been used against the Model class in
question.
If ``min_count`` is given, only tags which have a ``count`` greater
than or equal to ``min_count`` will be returned.
Passing a value for ``min_count`` implies ``counts=True``.
Basic usage
-----------
Tagging objects and retrieving an object's tags
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Objects may be tagged using the ``update_tags`` helper function::
>>> from shop.apps.products.models import Widget
>>> from tagging.models import Tag
>>> widget = Widget.objects.get(pk=1)
>>> Tag.objects.update_tags(widget, 'house thing')
Retrieve tags for an object using the ``get_for_object`` helper
function::
>>> Tag.objects.get_for_object(widget)
[, ]
Tags are created, associated and unassociated accordingly when you use
``update_tags`` and ``add_tag``::
>>> Tag.objects.update_tags(widget, 'house monkey')
>>> Tag.objects.get_for_object(widget)
[, ]
>>> Tag.objects.add_tag(widget, 'tiles')
>>> Tag.objects.get_for_object(widget)
[, , ]
Clear an object's tags by passing ``None`` or ``''`` to
``update_tags``::
>>> Tag.objects.update_tags(widget, None)
>>> Tag.objects.get_for_object(widget)
[]
Retrieving tags used by a particular model
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To retrieve all tags used for a particular model, use the
``get_for_model`` helper function::
>>> widget1 = Widget.objects.get(pk=1)
>>> Tag.objects.update_tags(widget1, 'house thing')
>>> widget2 = Widget.objects.get(pk=2)
>>> Tag.objects.update_tags(widget2, 'cheese toast house')
>>> Tag.objects.usage_for_model(Widget)
[, , , ]
To get a count of how many times each tag was used for a particular
model, pass in ``True`` for the ``counts`` argument::
>>> tags = Tag.objects.usage_for_model(Widget, counts=True)
>>> [(tag.name, tag.count) for tag in tags]
[('cheese', 1), ('house', 2), ('thing', 1), ('toast', 1)]
To get counts and limit the tags returned to those with counts above a
certain size, pass in a ``min_count`` argument::
>>> tags = Tag.objects.usage_for_model(Widget, min_count=2)
>>> [(tag.name, tag.count) for tag in tags]
[('house', 2)]
You can also specify a dictionary of `field lookups`_ to be used to
restrict the tags and counts returned based on a subset of the
model's instances. For example, the following would retrieve all tags
used on Widgets created by a user named Alan which have a size
greater than 99::
>>> Tag.objects.usage_for_model(Widget, filters=dict(size__gt=99, user__username='Alan'))
.. _`field lookups`: http://docs.djangoproject.com/en/dev/topics/db/queries/#field-lookups
The ``usage_for_queryset`` method allows you to pass a pre-filtered
queryset to be used when determining tag usage::
>>> Tag.objects.usage_for_queryset(Widget.objects.filter(size__gt=99, user__username='Alan'))
Tag input
---------
Tag input from users is treated as follows:
* If the input doesn't contain any commas or double quotes, it is simply
treated as a space-delimited list of tag names.
* If the input does contain either of these characters, we parse the
input like so:
* Groups of characters which appear between double quotes take
precedence as multi-word tags (so double quoted tag names may
contain commas). An unclosed double quote will be ignored.
* For the remaining input, if there are any unquoted commas in the
input, the remainder will be treated as comma-delimited. Otherwise,
it will be treated as space-delimited.
Examples:
====================== ======================================= ================================================
Tag input string Resulting tags Notes
====================== ======================================= ================================================
apple ball cat [``apple``], [``ball``], [``cat``] No commas, so space delimited
apple, ball cat [``apple``], [``ball cat``] Comma present, so comma delimited
"apple, ball" cat dog [``apple, ball``], [``cat``], [``dog``] All commas are quoted, so space delimited
"apple, ball", cat dog [``apple, ball``], [``cat dog``] Contains an unquoted comma, so comma delimited
apple "ball cat" dog [``apple``], [``ball cat``], [``dog``] No commas, so space delimited
"apple" "ball dog [``apple``], [``ball``], [``dog``] Unclosed double quote is ignored
====================== ======================================= ================================================
Tagged items
============
The relationship between a ``Tag`` and an object is represented by
the ``TaggedItem`` model, which lives in the ``tagging.models``
module.
API reference
-------------
Fields
~~~~~~
``TaggedItem`` objects have the following fields:
* ``tag`` -- The ``Tag`` an object is associated with.
* ``content_type`` -- The ``ContentType`` of the associated model
instance.
* ``object_id`` -- The id of the associated object.
* ``object`` -- The associated object itself, accessible via the
Generic Relations API.
Manager functions
~~~~~~~~~~~~~~~~~
The ``TaggedItem`` model has a custom manager which has the following
helper methods, which accept either a ``QuerySet`` or a ``Model``
class as one of their arguments. To restrict the objects which are
returned, pass in a filtered ``QuerySet`` for this argument:
* ``get_by_model(queryset_or_model, tag)`` -- creates a ``QuerySet``
containing instances of the specififed model which are tagged with
the given tag or tags.
* ``get_intersection_by_model(queryset_or_model, tags)`` -- creates a
``QuerySet`` containing instances of the specified model which are
tagged with every tag in a list of tags.
``get_by_model`` will call this function behind the scenes when you
pass it a list, so you can use ``get_by_model`` instead of calling
this method directly.
* ``get_union_by_model(queryset_or_model, tags)`` -- creates a
``QuerySet`` containing instances of the specified model which are
tagged with any tag in a list of tags.
.. _`get_related method`:
* ``get_related(obj, queryset_or_model, num=None)`` - returns a list of
instances of the specified model which share tags with the model
instance ``obj``, ordered by the number of shared tags in descending
order.
If ``num`` is given, a maximum of ``num`` instances will be returned.
Basic usage
-----------
Retrieving tagged objects
~~~~~~~~~~~~~~~~~~~~~~~~~
Objects may be retrieved based on their tags using the ``get_by_model``
manager method::
>>> from shop.apps.products.models import Widget
>>> from tagging.models import Tag
>>> house_tag = Tag.objects.get(name='house')
>>> TaggedItem.objects.get_by_model(Widget, house_tag)
[, ]
Passing a list of tags to ``get_by_model`` returns an intersection of
objects which have those tags, i.e. tag1 AND tag2 ... AND tagN::
>>> thing_tag = Tag.objects.get(name='thing')
>>> TaggedItem.objects.get_by_model(Widget, [house_tag, thing_tag])
[]
Functions which take tags are flexible when it comes to tag input::
>>> TaggedItem.objects.get_by_model(Widget, Tag.objects.filter(name__in=['house', 'thing']))
[]
>>> TaggedItem.objects.get_by_model(Widget, 'house thing')
[]
>>> TaggedItem.objects.get_by_model(Widget, ['house', 'thing'])
[]
Restricting objects returned
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Pass in a ``QuerySet`` to restrict the objects returned::
# Retrieve all Widgets which have a price less than 50, tagged with 'house'
TaggedItem.objects.get_by_model(Widget.objects.filter(price__lt=50), 'house')
# Retrieve all Widgets which have a name starting with 'a', tagged with any
# of 'house', 'garden' or 'water'.
TaggedItem.objects.get_union_by_model(Widget.objects.filter(name__startswith='a'),
['house', 'garden', 'water'])
Utilities
=========
Tag-related utility functions are defined in the ``tagging.utils``
module:
``parse_tag_input(input)``
--------------------------
Parses tag input, with multiple word input being activated and
delineated by commas and double quotes. Quotes take precedence, so they
may contain commas.
Returns a sorted list of unique tag names.
See `tag input`_ for more details.
``edit_string_for_tags(tags)``
------------------------------
Given list of ``Tag`` instances, creates a string representation of the
list suitable for editing by the user, such that submitting the given
string representation back without changing it will give the same list
of tags.
Tag names which contain commas will be double quoted.
If any tag name which isn't being quoted contains whitespace, the
resulting string of tag names will be comma-delimited, otherwise it will
be space-delimited.
``get_tag_list(tags)``
----------------------
Utility function for accepting tag input in a flexible manner.
If a ``Tag`` object is given, it will be returned in a list as its
single occupant.
If given, the tag names in the following will be used to create a
``Tag`` ``QuerySet``:
* A string, which may contain multiple tag names.
* A list or tuple of strings corresponding to tag names.
* A list or tuple of integers corresponding to tag ids.
If given, the following will be returned as-is:
* A list or tuple of ``Tag`` objects.
* A ``Tag`` ``QuerySet``.
``calculate_cloud(tags, steps=4, distribution=tagging.utils.LOGARITHMIC)``
--------------------------------------------------------------------------
Add a ``font_size`` attribute to each tag according to the frequency of
its use, as indicated by its ``count`` attribute.
``steps`` defines the range of font sizes - ``font_size`` will be an
integer between 1 and ``steps`` (inclusive).
``distribution`` defines the type of font size distribution algorithm
which will be used - logarithmic or linear. It must be one of
``tagging.utils.LOGARITHMIC`` or ``tagging.utils.LINEAR``.
Model Fields
============
The ``tagging.fields`` module contains fields which make it easy to
integrate tagging into your models and into the
``django.contrib.admin`` application.
Field types
-----------
``TagField``
~~~~~~~~~~~~
A ``CharField`` that actually works as a relationship to tags "under
the hood".
Using this example model::
class Link(models.Model):
...
tags = TagField()
Setting tags::
>>> l = Link.objects.get(...)
>>> l.tags = 'tag1 tag2 tag3'
Getting tags for an instance::
>>> l.tags
'tag1 tag2 tag3'
Getting tags for a model - i.e. all tags used by all instances of the
model::
>>> Link.tags
'tag1 tag2 tag3 tag4 tag5'
This field will also validate that it has been given a valid list of
tag names, separated by a single comma, a single space or a comma
followed by a space.
Form fields
===========
The ``tagging.forms`` module contains a ``Field`` for use with
Django's `forms library`_ which takes care of validating tag name
input when used in your forms.
.. _`forms library`: http://docs.djangoproject.com/en/dev/topics/forms/
Field types
-----------
``TagField``
~~~~~~~~~~~~
A form ``Field`` which is displayed as a single-line text input, which
validates that the input it receives is a valid list of tag names.
When you generate a form for one of your models automatically, using
the ``ModelForm`` class, any ``tagging.fields.TagField`` fields in your
model will automatically be represented by a ``tagging.forms.TagField``
in the generated form.
Generic views
=============
The ``tagging.views`` module contains views to handle simple cases of
common display logic related to tagging.
``tagging.views.tagged_object_list``
------------------------------------
**Description:**
A view that displays a list of objects for a given model which have a
given tag. This is a thin wrapper around the
``django.views.generic.list_detail.object_list`` view, which takes a
model and a tag as its arguments (in addition to the other optional
arguments supported by ``object_list``), building the appropriate
``QuerySet`` for you instead of expecting one to be passed in.
**Required arguments:**
* ``queryset_or_model``: A ``QuerySet`` or Django model class for the
object which will be listed.
* ``tag``: The tag which objects of the given model must have in
order to be listed.
**Optional arguments:**
Please refer to the `object_list documentation`_ for additional optional
arguments which may be given.
* ``related_tags``: If ``True``, a ``related_tags`` context variable
will also contain tags related to the given tag for the given
model.
* ``related_tag_counts``: If ``True`` and ``related_tags`` is
``True``, each related tag will have a ``count`` attribute
indicating the number of items which have it in addition to the
given tag.
**Template context:**
Please refer to the `object_list documentation`_ for additional
template context variables which may be provided.
* ``tag``: The ``Tag`` instance for the given tag.
.. _`object_list documentation`: http://docs.djangoproject.com/en/dev/ref/generic-views/#django-views-generic-list-detail-object-list
Example usage
~~~~~~~~~~~~~
The following sample URLconf demonstrates using this generic view to
list items of a particular model class which have a given tag::
from django.conf.urls.defaults import *
from tagging.views import tagged_object_list
from shop.apps.products.models import Widget
urlpatterns = patterns('',
url(r'^widgets/tag/(?P[^/]+)/$',
tagged_object_list,
dict(queryset_or_model=Widget, paginate_by=10, allow_empty=True,
template_object_name='widget'),
name='widget_tag_detail'),
)
The following sample view demonstrates wrapping this generic view to
perform filtering of the objects which are listed::
from myapp.models import People
from tagging.views import tagged_object_list
def tagged_people(request, country_code, tag):
queryset = People.objects.filter(country__code=country_code)
return tagged_object_list(request, queryset, tag, paginate_by=25,
allow_empty=True, template_object_name='people')
Template tags
=============
The ``tagging.templatetags.tagging_tags`` module defines a number of
template tags which may be used to work with tags.
Tag reference
-------------
tags_for_model
~~~~~~~~~~~~~~
Retrieves a list of ``Tag`` objects associated with a given model and
stores them in a context variable.
Usage::
{% tags_for_model [model] as [varname] %}
The model is specified in ``[appname].[modelname]`` format.
Extended usage::
{% tags_for_model [model] as [varname] with counts %}
If specified - by providing extra ``with counts`` arguments - adds a
``count`` attribute to each tag containing the number of instances of
the given model which have been tagged with it.
Examples::
{% tags_for_model products.Widget as widget_tags %}
{% tags_for_model products.Widget as widget_tags with counts %}
tag_cloud_for_model
~~~~~~~~~~~~~~~~~~~
Retrieves a list of ``Tag`` objects for a given model, with tag cloud
attributes set, and stores them in a context variable.
Usage::
{% tag_cloud_for_model [model] as [varname] %}
The model is specified in ``[appname].[modelname]`` format.
Extended usage::
{% tag_cloud_for_model [model] as [varname] with [options] %}
Extra options can be provided after an optional ``with`` argument, with
each option being specified in ``[name]=[value]`` format. Valid extra
options are:
``steps``
Integer. Defines the range of font sizes.
``min_count``
Integer. Defines the minimum number of times a tag must have
been used to appear in the cloud.
``distribution``
One of ``linear`` or ``log``. Defines the font-size
distribution algorithm to use when generating the tag cloud.
Examples::
{% tag_cloud_for_model products.Widget as widget_tags %}
{% tag_cloud_for_model products.Widget as widget_tags with steps=9 min_count=3 distribution=log %}
tags_for_object
~~~~~~~~~~~~~~~
Retrieves a list of ``Tag`` objects associated with an object and stores
them in a context variable.
Usage::
{% tags_for_object [object] as [varname] %}
Example::
{% tags_for_object foo_object as tag_list %}
tagged_objects
~~~~~~~~~~~~~~
Retrieves a list of instances of a given model which are tagged with a
given ``Tag`` and stores them in a context variable.
Usage::
{% tagged_objects [tag] in [model] as [varname] %}
The model is specified in ``[appname].[modelname]`` format.
The tag must be an instance of a ``Tag``, not the name of a tag.
Example::
{% tagged_objects comedy_tag in tv.Show as comedies %}